A Megasphaera fossil with a matryoshka—a bundle of smaller cells within the organism. LEI CHEN, SHUHAI XIAOPaleontologists have unearthed new remnants of a mysterious organism known as Megasphaera. The 600-million-year-old fossils, about 0.7 millimeters in diameter, were discovered in southern China’s Doushantuo Formation. Scientists from the Virginia Polytechnic Institute and the Chinese Academy of Sciences announced the finding last week (September 24) in Nature. Although the fossils are likely the remains of multicellular eukaryotes, it’s unclear whether they represent algae or early animals.
The fossils show groups of cells enclosed in a thick envelope. Fossils with varying numbers and sizes of cells may indicate different developmental stages. These patterns of cell division and differentiation, the researchers report, are strong evidence of multicellularity. The new fossils therefore contradict previous interpretations of Megasphaera as sulfur-oxidizing bacteria or single-celled protists.
Paleobiologists have agreed for nearly a decade that Megasphaera were multicellular, according to Nicholas Butterfield of the University of Cambridge, who was not involved in the study. This study reveals “some specimens that show some new features, but it's not clear what exactly they mean,” Butterfield told The Scientist in an e-mail. He also noted that evidence of multicellularity has been found in fossils more than twice as old as Megasphaera.
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